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Heterophile antibodies are IgM antibodies with affinity for sheep and horse red blood cells. They appear during the first week of infectious mononucleosis symptoms, 3–4 weeks after infection and return to undetectable levels 3 to 6 months after infection. Heterophile antibody is a fairly specific but insensitive test for EBV.
It will generally not be positive during the 4–6 week incubation period before the onset of symptoms. The highest amount of heterophile antibodies occurs 2 to 5 weeks after the onset of symptoms. [9] If positive, it will remain so for at least six weeks. [10] An elevated heterophile antibody level may persist up to 1 year. [9]
The heterophile antibody test, or monospot test, works by agglutination of red blood cells from guinea pigs, sheep and horses. This test is specific but not particularly sensitive (with a false-negative rate of as high as 25% in the first week, 5–10% in the second, and 5% in the third). [ 26 ]
The Forssman antigen is a glycolipid heterophile antigen found in certain animals like dogs, horses, cats, turtles and sheep, and enteric organisms such as pneumococci.In sheep, it is found on erythrocytes but not on tissue and organs, unlike hamsters and guinea pigs whose organ cells do carry the antigen.
Examples include high levels of syphilis antibodies in HIV patients or high levels of cryptococcal antigen leading to false negative tests in undiluted samples. [7] [8] This phenomenon is also seen in serological tests for Brucellosis. [citation needed] It may be seen in precipitation reactions.
A new study has found that low levels of one anti-inflammatory antibody — IgM anti-PC — are also associated with atherosclerosis and heart attacks in older women, while higher levels appear to ...
An example of helpful cross-reactivity is in heterophile antibody tests, which detect Epstein-Barr virus using antibodies with specificity for other antigens. Cross-reactivity is also a commonly evaluated parameter for the validation of immune and protein binding based assays such as ELISA and RIA .
The Weil–Felix test is an agglutination test for the diagnosis of rickettsial infections. It was first described in 1916. By virtue of its long history and of its simplicity, it has been one of the most widely employed tests for rickettsia on a global scale, despite being superseded in many settings by more sensitive and specific diagnostic tests.